System and method for diesel exhaust fluid demand monitor

ABSTRACT

Systems, apparatuses, and methods include a plurality of diesel exhaust fluid (DEF) dosing systems and a controller. The plurality of DEF dosing systems are in fluid communication with an exhaust gas stream and are structured to provide DEF to the exhaust gas stream. The controller is structured to: determine a commanded amount of DEF dispensed to the exhaust gas stream; determine an actual amount of DEF dispensed to the exhaust gas stream; determine a difference between the commanded amount of DEF and the actual amount of DEF; determine a value of a DEF variable indicative of an amount of DEF not dosed over a predetermined time period; compare the value of the DEF variable to a predetermined threshold; and indicate a fault alert in response to the value of the DEF variable exceeding the predetermined threshold.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority to U.S. Provisional Patent Application No. 62/742,631, filed Oct. 8, 2018, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to exhaust aftertreatment systems. More particularly, the present disclosure relates to diagnosing operation of exhaust aftertreatment systems.

BACKGROUND

Emissions regulations for internal combustion engines have become more stringent over recent years. Environmental concerns have motivated the implementation of stricter emission requirements for internal combustion engines throughout much of the world. Governmental agencies, such as the Environmental Protection Agency (EPA) in the United States, carefully monitor the emissions of engines and set acceptable emission standards, to which all engines must comply. Consequently, the use of exhaust aftertreatment systems on engines to reduce emissions is increasing.

Exhaust aftertreatment systems include diesel exhaust fluid (DEF) dispensing systems that inject a dose of a DEF into the exhaust gas stream. The DEF is configured to reduce nitrous oxides (NOx) in the exhaust gas stream into less harmful compounds. The DEF dispensing system can include pumps and DEF dosers that dispense the DEF into the exhaust gas stream. Although the DEF dispensing system can command the pumps and/or DEF dosers to inject a dose of DEF into the exhaust gas stream, the pumps and/or dosers may not actually dispense the dose of DEF into the exhaust gas stream. Over time, this can lead to the engine failing or potentially failing to meet emissions standards or other desired emissions requirements, such as that of a manufacturer.

SUMMARY

One embodiment relates to an apparatus. The apparatus includes a diesel exhaust fluid (DEF) command circuit, a dispensed DEF determination circuit, and a deficit determination circuit. The DEF command circuit is structured to determine a commanded amount of DEF dispensed to an exhaust gas stream. The dispensed DEF determination circuit is structured to determine an actual amount of DEF dispensed to the exhaust gas stream. The deficit determination circuit is structured to determine a difference between the commanded amount of DEF and the actual amount of DEF, determine a value of a DEF variable indicative of amount of DEF not dispensed over a predetermined time period, compare the value of the DEF variable to a predetermined threshold, and indicate a fault alert in response to the value of the DEF variable exceeding the predetermined threshold.

In some embodiments, the dispensed DEF determination circuit is structured to receive information indicative of a status of at least one DEF dosing system structured to dispense the commanded amount of DEF to the exhaust gas stream and determine the actual amount of DEF dispensed to the exhaust gas stream based on the information indicative of the status of the at least one DEF dosing system.

In some embodiments the actual amount of DEF dispensed is determined based on an amount of DEF dosing systems having a dosing status, an amount of time that the DEF dosing system having the dosing status are dispensing DEF, and a commanded flow rate of DEF.

In some embodiments, the apparatus further includes a compensation circuit structured to receive information indicative of a non-dosing status of at least one DEF dosing system of a plurality of DEF dosing systems structured to dispense the commanded amount of DEF to the exhaust gas stream and increase an amount of DEF dispensed by other DEF dosing systems of the plurality of DEF dosing systems in response to receiving the information indicative of the non-dosing status.

In some embodiments, in response to the DEF variable being a non-zero number and the difference being substantially zero, the deficit determination circuit is structured to decrement the DEF variable by a predetermined amount.

Another embodiment relates to a system. The system includes a plurality of diesel exhaust fluid (DEF) dosing systems in fluid communication with an exhaust gas stream and a controller. The plurality of DEF dosing systems is structured to provide DEF to the exhaust gas stream. The controller is structured to determine a commanded amount of DEF dispensed to the exhaust gas stream, determine an actual amount of DEF dispensed to the exhaust gas stream, determine a difference between the commanded amount of DEF and the actual amount of DEF, determine a value of a DEF variable indicative of an amount of DEF not dosed over a predetermined time period, compare the value of the DEF variable to a predetermined threshold, and indicate a fault alert in response to the value of the DEF variable exceeding the predetermined threshold.

In some embodiments, the controller is structured to receive information indicative of a status of at least one DEF dosing system of the plurality of DEF dosing systems and determine the actual amount of DEF dispensed to the exhaust gas stream based on the information indicative of the status of the at least one DEF dosing system.

In some embodiments, the actual amount of DEF dispensed is determined based on an amount of DEF dosing systems having a dosing status, an amount of time that the DEF dosing systems are dispensing DEF, and a commanded flow rate of DEF.

In some embodiments, the controller is further structured to receive information indicative of a non-dosing status of at least one DEF dosing system of the plurality of DEF dosing systems and increase an amount of DEF dispensed by other DEF dosing systems of the plurality of DEF dosing systems in response to receiving the information indicative of the non-dosing status.

In some embodiments, the controller is further structured to determine an amount of time that the actual amount of DEF is less than the commanded amount of DEF.

In some embodiments, the DEF variable is a cumulative volume of DEF that has not been dispensed.

In some embodiments, the controller is structured to decrement the DEF variable by a predetermined amount in response to the DEF variable being a non-zero number and the difference being substantially zero.

Still another embodiment relates to a method. The method includes determining a commanded amount of DEF dispensed to an exhaust gas stream by a plurality of diesel exhaust fluid (DEF) dosing systems in fluid communication with the exhaust gas stream, determining an actual amount of DEF dispensed to the exhaust gas stream by the plurality of DEF dosing systems, determining a difference between the commanded amount of DEF and the actual amount of DEF dispensed to the exhaust gas stream by the plurality of DEF dosing systems, determining a value of a DEF variable indicative of an amount of DEF not dispensed over a predetermined time period, comparing the value of the DEF variable to a predetermined threshold, and indicating a fault alert in response to the value of the DEF variable exceeding the predetermined threshold.

In some embodiments, the method further includes the steps of receiving information indicative of a status of at least one DEF dosing system of the plurality of DEF dosing systems and determining the actual amount of DEF dispensed to the exhaust gas stream based on the information indicative of the status of at least one of the DEF dosing systems.

In some embodiments, the actual amount of DEF dispensed is determined based on an amount of DEF dosing systems having an active status, an amount of time that the DEF dosing systems are dispensing DEF, and a commanded flow rate of DEF.

In some embodiments, the method further includes the steps of receiving information indicative of a non-dosing status of at least one DEF dosing system of the plurality of DEF dosing systems and increasing an amount of DEF dispensed by other DEF dosing systems of the plurality of DEF dosing systems in response to receiving the information indicative of the non-dosing status.

In some embodiments, the method further includes determining an amount of time that the actual amount of DEF is less than the commanded amount of DEF.

In some embodiments, the DEF variable is a cumulative volume of DEF that has not been dispensed.

These and other features, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram of a vehicle including an exhaust aftertreatment system with a controller, according to an example embodiment.

FIG. 2 is a schematic representation of a controller of the vehicle of FIG. 1, according to an example embodiment.

FIG. 3 illustrates a method for determining an effect of a cumulative amount of diesel exhaust fluid (DEF) not dispensed to an exhaust gas stream according to an example embodiment.

FIG. 4 illustrates flow diagram of a method for determining an amount of time that a cumulative amount of DEF not dispensed to an exhaust gas stream is at or above a predetermined threshold according to an example embodiment.

FIG. 5 illustrates a flow diagram of a method for determining an amount of time that a cumulative amount of DEF not dispensed to an exhaust gas stream is at or above a predetermined threshold according to another example embodiment.

FIG. 6 is a combined counter versus time plot and an amount of DEF not dispensed v.s. time plot illustrating a value of a timer indicative of an amount of time that a cumulative amount of DEF is not dispensed to an exhaust gas stream according to the method of FIG. 4 or 5.

FIG. 7 illustrates operation of a DEF dispensing system of the vehicle of FIG. 1 in which all pumps of a DEF dispensing system are pressurized according to an example embodiment.

FIG. 8 illustrates operation of a DEF dispensing system of the vehicle of FIG. 1 in which one of the pumps of a DEF dispensing system loses pressure for a period of time according to an example embodiment.

FIG. 9 illustrates operation of a DEF dispensing system of the vehicle of FIG. 1 in which two of the pumps of a DEF dispensing system loses pressure for a period of time according to an example embodiment.

FIG. 10 illustrates operation of a DEF dispensing system of the vehicle of FIG. 1 in which one of the pumps of a DEF dispensing system loses pressure for two periods of time according to an example embodiment.

DETAILED DESCRIPTION

Following below are more detailed descriptions of various concepts related to, and embodiments of methods, apparatuses, and systems for determining a difference between a commanded and an actual dose of diesel exhaust fluid (DEF) dispensed over a predetermined time period, summing the difference over the predetermined time period, and comparing the sum to a predetermined threshold. The sum is indicative of a cumulative amount of DEF that is not dispensed to the exhaust gas stream. If the sum is greater than a predetermined threshold, an insufficient amount of DEF has been dispensed relative to the engine out nitrous oxides (NOx). As such, the conversion of undesired NOx to less harmful compounds may be below a desired threshold. Therefore, identifying these potential situations is desirable. The various concepts introduced herein below may be implemented in any number of ways, as the concepts described are not limited to any particular manner of embodiment. Examples of specific embodiments and applications are provided primarily for illustrative purposes.

As described herein, a controller determines an amount of DEF for injecting into an exhaust gas stream (e.g., based on an engine out NOx amount, etc.). The controller commands DEF dosing systems of the exhaust aftertreatment system to dispense the commanded amount of DEF into the exhaust gas stream. In some circumstances, the DEF dosing systems dispense less than the commanded amount of DEF into the exhaust gas stream. This can occur, for example, when a pump in the DEF dosing system loses pressure (e.g., “drops out”) and/or when a doser in the DEF dosing system is blocked and/or drops out, which can cause the DEF dosing system to dispense less than the commanded amount of DEF into the exhaust gas stream.

The controller determines a cumulative difference between the commanded amount of DEF and the actual amount of DEF that is dispensed to the exhaust gas stream. The controller then determines the effect of the cumulative difference. For example, the controller can compare the cumulative difference to a predetermined threshold. When the cumulative difference is below the predetermined threshold, the system (vehicle and/or engine) is likely converting undesirable nitrous oxides to less harmful compounds before emission to the environment. As a result and when the cumulative difference is below the predefined threshold, compliance with one or more requirements, such as an emissions standard or a manufacturer's desired operating characteristic, may be met or substantially met. The controller does not notify the operator of pump and/or doser drop-outs that occur when the cumulative difference is below the predetermined threshold. When the cumulative difference is above the predetermined threshold, an unwanted consequence may occur, such as the system (vehicle and/or engine) not or possibly not meeting one or more requirements, such as an emissions standard. The controller notifies the operator, via an operator I/O interface, of this potential result/consequence/etc. Notifying the operator based on the value of the cumulative difference can reduce an amount of notifications displayed to an operator of the vehicle because the user is notified based on the cumulative effect of the pump and/or doser dropouts instead of being notified of every pump and/or doser dropout.

As shown in FIG. 1, a vehicle 10 including an engine system 14 including an engine 18 in exhaust gas-receiving communication with an exhaust gas processor or exhaust aftertreatment system 22, a controller 26, and an operator input/output (I/O) device 30 is depicted, according to an example embodiment. According to one embodiment and as shown, the engine 18 is structured as a compression-ignition internal combustion (IC) engine that utilizes diesel fuel. Within the internal combustion engine 18, air from the atmosphere is combined with fuel, and combusted, to power the engine. Combustion of the fuel and air in the compression chambers of the engine 18 produces exhaust gas that is operatively vented to the exhaust aftertreatment system 22.

Returning to FIG. 1, the exhaust aftertreatment system 22 includes a selective catalytic reduction (SCR) system 46 with an SCR catalyst 50. In some embodiments, the aftertreatment system 22 can further include a diesel particulate filter (DPF) 38, a diesel oxidation catalyst (DOC) 42, and an ammonia oxidation (AMOx) catalyst 54. The SCR system 46 further includes a DEF dispensing system that has a diesel exhaust fluid (DEF) source 58 that supplies DEF to a doser 62 via a DEF dispensing line 64.

In an exhaust flow direction, as indicated by directional arrow 66, exhaust gas flows into inlet piping 70 of the exhaust aftertreatment system 22. In embodiments that include the DPF 38 and the DOC 42, from the inlet piping 70, the exhaust gas flows into the DOC 42 and exits the DOC 42 into a first section of exhaust piping 74A. From the first section of exhaust piping 74A, the exhaust gas flows into the DPF 38 and exits the DPF 38 into a second section of exhaust piping 74B. From the second section of exhaust piping 74B, the exhaust gas flows into the SCR catalyst 50 and exits the SCR catalyst 50 into the third section of exhaust piping 74C. As the exhaust gas flows through the second section of exhaust piping 74B, it is periodically dosed with DEF by the DEF doser 62. Accordingly, the second section of exhaust piping 74B acts as a decomposition chamber or tube to facilitate the decomposition of the DEF to ammonia. In embodiments that include the AMOx catalyst 54, from the third section of exhaust piping 74C, the exhaust gas flows into the AMOx catalyst 54 and exits the AMOx catalyst 54 into the outlet piping 78 before the exhaust gas is expelled from the exhaust aftertreatment system 22. In embodiments that do not include the DPF 38 and the DOC 42, the exhaust gas flows to the SCR catalyst 50. Based on the foregoing, in the illustrated embodiment, the SCR catalyst 50 is positioned upstream of the AMOx catalyst 54. However, in alternative embodiments, other arrangements of the components of the exhaust aftertreatment system 22 are also possible (e.g., the AMOx catalyst 54 may be excluded from the exhaust aftertreatment system 22).

As discussed above and in this example configuration, the SCR system 46 includes a first DEF dispensing system 82 and a second DEF dispensing system 86. The first DEF dispensing system 82 and the second DEF dispensing system 86 are substantially similar. Like parts between the first DEF dispensing system 82 and the second DEF dispensing system 86 are denoted with the prime symbol “′” for the second DEF dispensing system 86. The first DEF dispensing system 82 includes the DEF source 58 and a plurality of DEF dosing systems 90. The DEF source can be a container or tank capable of retaining DEF. DEF (e.g., urea) is used as an exemplary reductant through the disclosure. However, it is also contemplated that other reductants, such as, for example, ammonia (NH3), or diesel oil can be used. The DEF source is in DEF supplying communication with the plurality of DEF dosing systems 90. Each of the plurality of DEF dosing systems 90 includes a pump 94 and a dosing mechanism or doser 62. The pump 94 is configured to pump DEF from the DEF source to the doser 62 via the DEF dispensing line 64. In the illustrated embodiment, the plurality of DEF dosing systems 90 includes three DEF dosing systems 90. In other embodiments, the plurality of DEF dosing systems 90 may include more or fewer DEF dosing systems. A pressure sensor 102 is engaged with each pump 94 and configured to sense a pressure of the pump 94. A doser sensor 106 is engaged with each doser 62. The doser sensors 106 are configured to sense a pressure and/or a blockage of the doser 62. The plurality of DEF dosing systems 90 are positioned upstream of the SCR catalyst 50. Each DEF dosing system 90 is selectively controllable (e.g., by the controller 26) to inject DEF directly into the exhaust gas stream prior to entering the SCR catalyst 50. As described herein, the controller 26 is structured to control the timing and amount of the DEF dispensed to the exhaust gas. As described above, the ammonia reacts with NOx in the presence of the SCR catalyst 50 to reduce the NOx to less harmful emissions, such as N2 and H2O. The NOx in the exhaust gas stream includes NO2 and NO. Generally, both NO2 and NO are reduced to N2 and H2O through various chemical reactions driven by the catalytic elements of the SCR catalyst 50 in the presence of NH3.

Returning to FIG. 1, the SCR catalyst 50 may be any of various catalysts known in the art. For example, in some embodiments, the SCR catalyst 50 is a vanadium-based catalyst, and in other embodiments, the SCR catalyst 50 is a zeolite-based catalyst, such as a Cu-Zeolite or a Fe-Zeolite catalyst. In one representative embodiment, the DEF is aqueous urea and the SCR catalyst 50 is a vanadium-based catalyst.

The AMOx catalyst 54 may be any of various flow-through catalysts configured to react with ammonia to produce mainly nitrogen. As briefly described above, the AMOx catalyst 54 is structured to remove ammonia that has slipped through or exited the SCR catalyst 50 without reacting with NOx in the exhaust. In certain instances, the exhaust aftertreatment system 22 can be operable with or without the AMOx catalyst 54. Further, although the AMOx catalyst 54 is shown as a separate unit from the SCR catalyst 50 in FIG. 1, in some embodiments, the AMOx catalyst 54 may be integrated with the SCR catalyst 50, e.g., the AMOx catalyst 54 and the SCR catalyst 50 can be located within the same housing.

Various sensors, such as NOx sensors and temperature sensors, may be strategically disposed throughout the exhaust aftertreatment system 22 and may be in communication with the controller 26 to monitor operating conditions of the engine system 14. In this regard, the controller 26 may receive data from the one or more sensors. As shown in FIG. 1, the exhaust aftertreatment system 22 includes a temperature sensor 110, a temperature sensor 114, a NOx sensor 118, and a NOx sensor 122. The temperature sensor 110 is associated with an engine coolant system for determining a temperature at or proximate an outlet of the engine coolant system. The temperature sensor 114 is positioned between an exhaust outlet of the engine and an inlet of the SCR system 46 for determining the temperature of the exhaust gas stream as or before the exhaust gas stream enters the SCR system 46. The NOx sensor 118 is positioned proximate and/or at the inlet of the SCR system 46 for determining a NOx concentration of the exhaust gas stream entering the SCR system 46. The NOx sensor 122 is positioned at and/or proximate an outlet of the SCR system 46 to determine a NOx concentration of the exhaust gas stream leaving the SCR system 46.

Although the exhaust aftertreatment system 22 shown includes one of an SCR catalyst 50 and AMOx catalyst 54 positioned in specific locations relative to each other along the exhaust flow path, in other embodiments, the exhaust aftertreatment system 22 may include more than one of any of the various catalysts positioned in any of various positions relative to each other along the exhaust flow path as desired. Further, although the DOC 42 and AMOx catalyst 54 are non-selective catalysts, in some embodiments, the DOC 42 and AMOx catalyst 54 can be selective catalysts.

The DOC 42 may have any of various flow-through designs. Generally, the DOC 42 is structured to oxidize at least some particulate matter, e.g., the soluble organic fraction of soot, in the exhaust and reduce unburned hydrocarbons and CO in the exhaust to less environmentally harmful compounds. For example, the DOC 42 may be structured to reduce the hydrocarbon and CO concentrations in the exhaust to meet or likely meet the requisite emissions standards for those components of the exhaust gas. An indirect consequence of the oxidation capabilities of the DOC 42 is the ability of the DOC 42 to oxidize NO into NO2. In this manner, the level of NO2 exiting the DOC 42 is equal to the NO2 in the exhaust gas generated by the engine 18 plus the NO2 converted from NO by the DOC 42.

The DPF 38 may be any of various flow-through designs, and is structured to reduce particulate matter concentrations, e.g., soot and ash, in the exhaust gas to meet or likely meet one or more requisite emission standards. The DPF 38 captures particulate matter and other constituents, and thus needs to be periodically regenerated to burn off the captured constituents. Additionally, the DPF 38 may be configured to oxidize NO to form NO2 independent of the DOC 42.

Based on the foregoing, in the illustrated embodiment, the DOC 42 is positioned upstream of the DPF 38 and the SCR catalyst 50, and the SCR catalyst 50 is positioned downstream of the DPF 38 and upstream of the AMOx catalyst 54. However, in alternative embodiments, other arrangements of the components of the exhaust aftertreatment system 22 are also possible (e.g., the AMOx catalyst 54 may be excluded from the exhaust aftertreatment system 22). For example, in some embodiments, the exhaust aftertreatment system 22 can include one of the DOC 42 and the DPF 38. In other embodiments, the exhaust aftertreatment system 22 can include neither the DOC 42 nor the DPF 38. In such embodiments, the vehicle components are positioned in conjunction with the principles described above.

FIG. 1 is also shown to include the operator I/O device 30. The operator I/O device 30 is communicably coupled to the controller 26, such that information may be exchanged between the controller 26 and the operator I/O device 30, wherein the information may relate to one or more components of FIG. 1 or determinations/commands/instructions/etc. (described below) of the controller 26. The operator I/O device 30 enables an operator of the vehicle (or another passenger) to communicate with the controller 26 and one more components of the vehicle and components of FIG. 1. For example, the operator I/O device 30 may include, but is not limited to, an interactive display, a touchscreen device, one or more buttons and switches, voice command receivers, etc. Via the operator I/O device 30, the controller 26 may provide various information concerning the operations described herein.

The controller 26 is structured to control, at least partly, the operation of the engine system 14 and associated sub-systems, such as the internal combustion engine 18 and the exhaust aftertreatment system 22. According to one embodiment, the components of FIGS. 1-2 are embodied in the vehicle 10. The vehicle 10 may include an on-road or an off-road vehicle including, but not limited to, line-haul trucks, mid-range trucks (e.g., pick-up trucks), tanks, airplanes, and any other type of vehicle that utilizes an SCR system. Communication between and among the components may be via any number of wired or wireless connections. For example, a wired connection may include a serial cable, a fiber optic cable, a CAT5 cable, or any other form of wired connection. In comparison, a wireless connection may include the Internet, Wi-Fi, cellular, radio, etc. In one embodiment, a controller area network (CAN) bus provides the exchange of signals, information, and/or data. The CAN bus includes any number of wired and wireless connections. Because the controller 26 is communicably coupled to the systems and components of FIG. 1, the controller 26 is structured to receive data from one or more of the components shown in FIG. 1. For example, the data may include temperature data, (e.g., a temperature of the engine coolant proximate the engine coolant outlet from temperature sensor 110 and a temperature of the exhaust gas at or before the inlet of the SCR system 46), NOx data (e.g., an incoming NOx amount from NOx sensor 118 and an outgoing NOx amount from NOx sensor 122), dosing data (e.g., timing and amount of dosing dispensed from the plurality of dosers 62), and vehicle operating data (e.g., engine speed, engine temperature, engine coolant temperature, exhaust temperature, etc.) received via one or more sensors. As another example, the data may include an input from operator I/O device 30. The structure and function of the controller 26 is further described in regard to FIG. 2.

Referring now to FIG. 2, a schematic diagram of the controller 26 of the vehicle of FIG. 1 is shown according to an example embodiment. As shown in FIG. 2, the controller 26 includes a processing circuit 126 having a processor 130 and a memory device 134, a DEF command circuit 138, a dispensed DEF determination circuit 142, a deficit determination circuit 146, a compensation circuit 150, and a communications interface 154. Generally, the controller 26 is structured to a) determine a cumulative difference between a commanded amount of DEF dispensed to the exhaust gas stream and an actual amount of DEF dispensed to the exhaust gas stream over a predetermined time period, and b) determine, an effect of the cumulative difference. For example, the cumulative difference can indicate whether enough DEF is dispensed to the exhaust gas stream for the vehicle to meet or likely meet a requirement, such as a NOx emissions standard. In response to determining, based on the cumulative difference, that an unwanted consequence may occur, such as the engine not or possibly not meeting one or more emissions standards, the controller is structured to display an error to an operator of the vehicle.

In one configuration, the DEF command circuit 138, the dispensed DEF determination circuit 142, the deficit determination circuit 146, and the compensation circuit 150 are embodied as machine or computer-readable media that is executable by a processor, such as the processor 130. As described herein and amongst other uses, the machine-readable media facilitates performance of certain operations to enable reception and transmission of data. For example, the machine-readable media may provide an instruction (e.g., command, etc.) to, e.g., acquire data from a particular physical sensor or a particular virtual sensor. In this regard, the machine-readable media may include programmable logic that defines the frequency of acquisition of the data (or, transmission of the data). The computer readable media may include code, which may be written in any programming language including, but not limited to, Java or the like and any conventional procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program code may be executed on one processor or multiple remote processors. In the latter scenario, the remote processors may be connected to each other through any type of network (e.g., CAN bus, etc.).

In another configuration, the DEF command circuit 138, the dispensed DEF determination circuit 142, the deficit determination circuit 146, and the compensation circuit 150 are embodied as hardware units, such as electronic control units. As such, the DEF command circuit 138, the dispensed DEF determination circuit 142, the deficit determination circuit 146, and the compensation circuit 150 may be embodied as one or more circuitry components including, but not limited to, processing circuitry, network interfaces, peripheral devices, input devices, output devices, sensors, etc. In some embodiments, the DEF command circuit 138, the dispensed DEF determination circuit 142, the deficit determination circuit 146, and the compensation circuit 150 may take the form of one or more analog circuits, electronic circuits (e.g., integrated circuits (IC), discrete circuits, system on a chip (SOCs) circuits, microcontrollers, etc.), telecommunication circuits, hybrid circuits, and any other type of “circuit.” In this regard, the DEF command circuit 138, the dispensed DEF determination circuit 142, the deficit determination circuit 146, and the compensation circuit 150 may include any type of component for accomplishing or facilitating achievement of the operations described herein. For example, a circuit as described herein may include one or more transistors, logic gates (e.g., NAND, AND, NOR, OR, XOR, NOT, XNOR, etc.), resistors, multiplexers, registers, capacitors, inductors, diodes, wiring, and so on). The DEF command circuit 138, the dispensed DEF determination circuit 142, the deficit determination circuit 146, and the compensation circuit 150 may also include programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like. The DEF command circuit 138, the dispensed DEF determination circuit 142, the deficit determination circuit 146, and the compensation circuit 150 may include one or more memory devices for storing instructions that are executable by the processor(s) of the DEF command circuit 138, the dispensed DEF determination circuit 142, the deficit determination circuit 146, and the compensation circuit 150. The one or more memory devices and processor(s) may have the same definition as provided herein with respect to the memory device 134 and the processor 130. In some hardware unit configurations, the DEF command circuit 138, the dispensed DEF determination circuit 142, the deficit determination circuit 146, and the compensation circuit 150 may be geographically dispersed throughout separate locations in the vehicle. Alternatively and as shown, the DEF command circuit 138, the dispensed DEF determination circuit 142, the deficit determination circuit 146, and the compensation circuit 150 may be embodied in or within a single unit/housing, which is shown as the controller 26.

In the example shown, the controller 26 includes a processing circuit 126 having the processor 130 and the memory device 134. The processing circuit 126 may be structured or configured to execute or implement the instructions, commands, and/or control processes described herein with respect to the DEF command circuit 138, the dispensed DEF determination circuit 142, the deficit determination circuit 146, and the compensation circuit 150. Thus, the depicted configuration represents the DEF command circuit 138, the dispensed DEF determination circuit 142, the deficit determination circuit 146, and the compensation circuit 150 as machine or computer-readable media. However, as mentioned above, this illustration is not meant to be limiting as the present disclosure contemplates other embodiments where the DEF command circuit 138, the dispensed DEF determination circuit 142, the deficit determination circuit 146, and the compensation circuit 150 or at least one circuit of the DEF command circuit 138, the dispensed DEF determination circuit 142, the deficit determination circuit 146, and the compensation circuit 150 is configured as hardware units. All such combinations and variations are intended to fall within the scope of the present disclosure.

The processor 130 may be implemented as one or more general-purpose processors, an application specific integrated circuit (ASIC), one or more field programmable gate arrays (FPGAs), a digital signal processor (DSP), a group of processing components, or other suitable electronic processing components. In some embodiments, the one or more processors may be shared by multiple circuits (e.g., the DEF command circuit 138, the dispensed DEF determination circuit 142, the deficit determination circuit 146, and the compensation circuit 150 may comprise or otherwise share the same processor which, in some example embodiments, may execute instructions stored, or otherwise accessed, via different areas of memory). Alternatively or additionally, the one or more processors may be structured to perform or otherwise execute certain operations independent of one or more co-processors. In other example embodiments, two or more processors may be coupled via a bus to enable independent, parallel, pipelined, or multi-threaded instruction execution. All such variations are intended to fall within the scope of the present disclosure. The memory device 134 (e.g., RAM, ROM, Flash Memory, hard disk storage, etc.) may store data and/or computer code for facilitating the various processes described herein. The memory device 134 may be communicably connected to the processor 130 to provide computer code or instructions to the processor 130 for executing at least some of the processes described herein. Moreover, the memory device 134 may be or include tangible, non-transient volatile memory or non-volatile memory. Accordingly, the memory device 134 may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described herein.

The communications interface 154 may be/include any combination of wired or wireless interfaces (e.g., jacks, antennas, transmitters, receivers, transceivers, wire terminals, etc.) for conducting data communications with various systems, devices, or networks. For example, the communications interface 154 may include an Ethernet card and port for sending and receiving data via an Ethernet-based communications network and/or a Wi-Fi transceiver for communicating via a wireless communications network. The communications interface 154 may be structured to communicate via local area networks or wide area networks (e.g., the Internet, etc.) and may use a variety of communications protocols (e.g., IP, LON, Bluetooth, ZigBee, radio, cellular, near field communication, etc.).

The communications interface 154 of the controller 26 may facilitate communication between and among the controller 26 and one or more components of the vehicle (e.g., components of vehicle subsystems (such as the engine system 14, the exhaust aftertreatment system 22), the operator I/O device 30, the sensors, etc.). Communication between and among the controller 26 and the components of the vehicle may be via any number of wired or wireless connections (e.g., any standard under IEEE 802, etc.). For example, a wired connection may include a serial cable, a fiber optic cable, a CAT5 cable, or any other form of wired connection. In comparison, a wireless connection may include the Internet, Wi-Fi, cellular, Bluetooth, ZigBee, radio, etc. In one embodiment, a controller area network (CAN) bus provides the exchange of signals, information, and/or data. The CAN bus can include any number of wired and wireless connections that provide the exchange of signals, information, and/or data. The CAN bus may include a local area network (LAN), or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

The DEF command circuit 138 is structured to receive information indicative of a concentration of NOx in the exhaust gas stream. Information indicative of the concentration of NOx in the exhaust gas stream can include information indicative of engine operating conditions or a NOx concentration of the exhaust gas stream determined by the NOx sensor 118 or based on data acquired by the NOx sensor 118. The DEF command circuit 138 is structured to determine a commanded amount of DEF to dispense to the exhaust gas stream based on the information indicative of the NOx concentration of the exhaust gas stream. The DEF command circuit 138 is structured to generate a dosing command to command each of the plurality of DEF dosing systems 90 to dispense the commanded amount of DEF to the exhaust gas stream. The dosing command can include a DEF flow rate and a dispensing time. The DEF command circuit 138 can allocate the commanded amount of DEF between the plurality of DEF dosing systems 90. In some embodiments, the DEF command circuit 138 can substantially evenly allocate the commanded amount of DEF to be dispensed between the plurality of DEF dosing systems 90. In other embodiments, the DEF command circuit 138 can allocate the amount of DEF dispensed by each of the plurality of DEF dosing systems 90 based on a status of each the plurality of DEF dosing systems 90. The status can be a dosing status, which indicates that the DEF dosing system 90 can dispense DEF (e.g., has sufficient pressure and/or is unblocked). The status can be a non-dosing status, which indicates that the DEF dosing system 90 cannot dispense DEF (e.g., has insufficient pressure and/or is blocked). For example, in response to receiving a fault indicating that one or more of the DEF dosing systems 90 has the non-dosing status, the DEF command circuit 138 can allocate the amount of dispensed DEF between the other DEF dosing systems 90 that have the dosing status.

The dispensed DEF determination circuit 142 is structured to determine an actual amount of DEF dispensed into the exhaust gas stream based on information indicative of an amount of NOx dispensed by each of the plurality of DEF dosing systems 90. The information indicative of the amount of NOx dispensed by the each of the plurality of DEF dosing systems 90 can include the status of each of the DEF dosing systems 90, an amount of time that each of the plurality of DEF dosing systems 90 dispensed DEF, and a commanded flow rate of DEF dispensed from each of the plurality of DEF dosing systems 90. In some embodiments, the dispensed DEF determination circuit 142 can determine the status of the DEF dosing systems 90 based on a pressure of each of the plurality of pumps 94 determined by the pressure sensors 102, a pressure and/or a presence of a blockage of each of the dosers 62 determined by the doser sensors 106, or both the pressure of the pumps 94 and the pressure and/or the presence of the blockage in the dosers 62.

The dispensed DEF determination circuit 142 can receive the dosing command from the DEF command circuit 138. The dispensed DEF determination circuit 142 can then multiply the commanded flow rate by the dispensing time for each of the DEF dosing systems 90 having the dosing status to determine an amount of DEF dispensed by each of the DEF dosing systems 90 having the dosing status. The dispensed DEF determination circuit 142 can assume that each of the DEF dosing systems 90 having the non-dosing status dispense substantially no DEF. The dispensed DEF determination circuit 142 can then sum the amount of DEF dispensed by each of the dosers 62 to determine the actual amount of DEF dispensed into the exhaust gas stream.

For example, the dispensed DEF determination circuit 142 can receive information indicative of a status of each of the plurality of pumps 94. In some embodiments, the information indicative of the status of each of the plurality of pumps 94 can include a pressure of each of the plurality of pumps 94 determined by the pressure sensors 102. The dispensed DEF determination circuit 142 can determine a status of each of the pumps 94 based on the pressure of the pumps 94 relative to a predetermined pump pressure threshold. For example, the dispensed DEF determination circuit 142 can determine that any of the pumps 94 having a pressure below the pump pressure threshold have the non-dosing status. For example, in some embodiments, the pump pressure threshold is a pressure below substantially 650 kPa that has lasted for at least 200 seconds. The dispensed DEF determination circuit 142 can determine that any of the pumps 94 having a pressure above a pump pressure threshold have the dosing status. The dispensed DEF determination circuit can determine the status of each of the plurality of dosers 62 in a similar manner.

The deficit determination circuit 146 is structured to receive the commanded amount of DEF dispensed to the exhaust gas stream from the DEF command circuit 138 and to receive the actual amount of DEF dispensed to the exhaust gas stream from the dispensed DEF determination circuit 142. The deficit determination circuit 146 is structured to determine a difference between the commanded amount of DEF and the actual amount of DEF dispensed into the exhaust gas stream. For example, the deficit determination circuit 146 may subtract the actual amount of DEF dispensed from the commanded amount of DEF dispensed. Accordingly, during operating conditions in which the actual amount of DEF dispensed is less than the commanded amount of DEF dispensed, the difference is a positive value. During operating conditions in which the actual amount of DEF dispensed is greater than the commanded amount of DEF dispensed, the difference is a negative value. The deficit determination circuit 146 is structured to increment a DEF variable by the difference. Accordingly, a value of the DEF variable increases when the actual amount of DEF dispensed is less than the commanded amount of DEF dispensed and the value of the DEF variable decreases when the actual amount of DEF dispensed is greater than the commanded amount of DEF dispensed.

In some embodiments, the DEF variable may be a running (e.g., cumulative) sum of the differences between the commanded amount and the actual amount of DEF dispensed over a predetermined time period. The DEF variable is indicative of an amount of DEF that is not dispensed to the exhaust gas stream for the predetermined time period (e.g., by DEF dosing systems 90 having the non-dosing status failing to deliver the commanded amount of DEF) during the time period. For example, if one or more of the plurality of the pumps 94 have low pressure (e.g., experience pump dropout), the actual amount of DEF dispensed to the exhaust gas stream by the first DEF dispensing system 82 can be less than the commanded amount of DEF. In another example, if one or more of the plurality of dosers 62 has low pressure and/or is blocked, the actual amount of DEF dispensed to the exhaust gas stream by the first DEF dispensing system 82 can be less than the commanded amount of DEF.

By way of non-limiting example, the commanded amount of DEF may be 10 mL delivered once every 10 seconds, the predetermined time period may be 30 seconds, and the initial value of the DEF variable is 0 mL. Accordingly, the commanded amounts of DEF delivered over the predetermined time period are 10 mL, 10 mL, and 10 mL. The exemplary actual amounts of DEF delivered over the predetermined period are 10 mL, 8 mL, and 9 mL. The difference for each dose is determined by subtracting the commanded dose by the actual dose, yielding differences of 0 mL, 2 mL, and 1 mL. After each dose, the difference is added to the DEF variable. Therefore, after the first dose, the value of the DEF variable is 0 mL. After the second dose, the value of the DEF variable is 2 mL. After the third dose, the value of the DEF variable is 3 mL.

In another non-limiting example, the commanded amount of DEF may be 10 mL delivered once every 10 seconds, the predetermined time period may be 30 seconds, and the initial value of the DEF variable is 0 mL. Accordingly, the commanded amounts of DEF delivered over the predetermined time period are 10 mL, 10 mL, and 10 mL. The exemplary actual amounts of DEF delivered over the predetermined period are 10 mL, 7 mL, and 11 mL. The difference for each dose is determined by subtracting the commanded dose by the actual dose, yielding differences of 0 mL, 3 mL, and −1 mL. After each dose, the difference is added to the DEF variable. Therefore, after the first dose, the value of the DEF variable is 0 mL. After the second dose, the value of the DEF variable is 3 mL. After the third dose, the value of the DEF variable is 2 mL.

The deficit determination circuit 146 is structured to compare the DEF variable to a predetermined threshold (e.g. upper bound). The predetermined threshold is a value or range of values of DEF that has not been dispensed at which an unwanted consequence may occur, such as the engine 18 not or possibly not meeting one or more emissions standards or desired operating characteristics/parameters of the aftertreatment system 22. The predetermined threshold can be determined based on emissions standards, engine duty cycle, engine efficiency, number of dosers 62, and/or number of pumps 94. In response to determining that the DEF variable (e.g., cumulative amount of DEF that has not been dispensed) is less than the predetermined threshold, the deficit determination circuit 146 determines that enough DEF has been dispensed for the vehicle 10 to meet or likely meet a desired operating parameter, such as a NOx emissions standard(s). In response to determining that the DEF variable is greater than or equal to the predetermined threshold, the deficit determination circuit 146 is structured to determine that an unwanted consequence may occur, such as the engine 18 not or possibly not meeting one or more emissions standards. The deficit determination circuit 146 is then structured to set a fault indicating that the DEF variable exceeds the predetermined threshold. The deficit determination circuit 146 is structured to notify the operator of the vehicle 10 of the fault via the operator I/O device 30.

The DEF deficits can be temporary and may not cause a negative consequence to occur, such as the engine 18 not or possibly not meeting one or more emissions standards. Therefore, the controller 26 sets the fault based on the value of the DEF variable; notifications are sent to the operator via the operator I/O device 30 when an unwanted consequence may occur, such as the engine 18 not or possibly not meeting one or more emissions standards. This is in contrast to alerting the user of every instance that any of the DEF dosing systems 90 are in the non-dosing status. Furthermore, conditions that lead to any of the DEF dosing systems 90 having the non-dosing status may be self-correcting (e.g., pump pressure increases, air bubbles and/or other blockages in the dosers 62 pass, etc.) and may not require user action. Therefore, fault notifications based on the value of the DEF variable can reduce an amount of fault notifications displayed to the operator, some of which are not indicative that an unwanted consequence may occur, such as the engine 18 not or possibly not meeting one or more emissions standards and/or do not require user action.

In some embodiments, the deficit determination circuit 146 is structured to decrement a value of the DEF variable by a decrement value in response to the actual amount of DEF injected into the exhaust gas stream being substantially the same as the commanded amount of DEF over a predetermined time interval. Decrementing the value of the DEF variable by the decrement value allows the DEF variable to be corrected to simulate recovery (e.g., repressurization, clearing of a blockage) of any of the DEF dosing systems 90 that had previously dropped out. In some embodiments, the predetermined time interval can be a value or an acceptable range of values. In some embodiments, the deficit determination circuit 146 is structured to decrement a value of the difference by a value of a leak variable. The leak variable is sized to represent leaking of DEF from the DEF dosing systems 90 when the DEF dosing systems 90 are not actively dispensing DEF into the exhaust gas stream. In some embodiments, the leak variable can be a value or an acceptable range of values

Referring now to FIG. 3, a method 160 for determining a cumulative amount of DEF that is not dispensed to an exhaust gas stream and for determining an effect of the cumulative amount of DEF that is dispensed to the exhaust gas stream is shown according to an example embodiment. At process 162, the DEF command circuit 138 receives information indicative of a concentration of NOx in the exhaust gas stream. At process 166, the DEF command circuit 138 determines a commanded amount of DEF to dispense to the exhaust gas stream. At process 170, the DEF command circuit 138 may allocate the commanded amount of DEF between DEF dosing systems 90. At process 174, the DEF command circuit 138 sends the dosing command to each of the plurality of DEF dosing systems 90.

At process 178, the dispensed DEF determination circuit 142 receives information indicative of the status of each of the DEF dosing systems 90. For example, the dispensed DEF determination circuit 142 can receive information indicative of the pressure of each of the pumps 94 from the pressure sensors 102 and/or information indicative of a pressure and/or a blockage of each of the dosers 62 from the doser sensors 106. At process 182, the dispensed DEF determination circuit 142 determines the status of each of the dosing systems 90. At process 186, the dispensed DEF determination circuit 142 receives information indicative of the actual amount of DEF dispensed into the exhaust gas stream by the DEF dosing systems 90. At process 190, the dispensed DEF determination circuit 142 determines the actual amount of DEF dispensed into the exhaust gas stream based on the information indicative of the amount of DEF dispensed into the exhaust gas stream. For example, the dispensed DEF determination circuit 142 may determine the actual amount of DEF dispensed into the exhaust gas stream based on an amount of DEF dosing systems 90 that have the dosing status, the commanded flow rate, and the length of time that DEF dosing systems 90 are dispensing DEF.

At process 194, the deficit determination circuit 146 determines the difference between the commanded amount of DEF dispensed into the exhaust gas stream and the actual amount of DEF dispensed into the exhaust gas stream. At process 198, the deficit determination circuit 146 increments the DEF variable by the difference between the commanded amount of DEF and the actual amount of DEF dispensed to the exhaust gas stream. At process 202, the deficit determination circuit 146 compares the DEF variable to the predetermined threshold. At process 206, in response to determining that the DEF variable is less than the predetermined threshold, the deficit determination circuit 146 determines that the first DEF dispensing system 82 is likely dispensing enough DEF to the exhaust gas stream to meet or likely meet one or more desired operating characteristics, such as an emissions standard. At process 210, the deficit determination circuit 146 determines whether the DEF variable has a non-zero value. The DEF variable has a non-zero value when the actual amount of DEF dispensed into the exhaust gas stream has previously been below the commanded amount of DEF, and the DEF variable (which is indicative of the cumulative amount of DEF not dosed) is still compensating for the cumulative amount of DEF not dosed during the DEF dosing system dropout. The DEF variable has a zero value when the difference between the actual amount of DEF the cumulative amount of DEF not dosed is substantially zero. In response to determining that the difference variable has a value of zero, the method 160 then returns to process 162. At process 214, in response to determining that the deficit variable has a non-zero value, the deficit determination circuit subtracts the decrement value from the value of the DEF variable. The method 160 then returns to process 162. At process 218, in response to determining that the DEF variable is greater than or equal to the predetermined threshold, the deficit determination circuit 146 determines that an unwanted consequence may occur, such as the engine not or possibly not meeting one or more emissions standards. At process 222, the deficit determination circuit 146 sets a fault indicating that an unwanted consequence may occur, such as the engine not or possibly not meeting one or more emissions standards. At process 226, the deficit determination circuit 146 can display an indication of the fault to an operator via the operator I/O device 30. The method 160 then returns to process 162.

In some embodiments, the compensation circuit 150 is structured to receive the status (e.g., dosing or non-dosing) of each of the DEF dosing systems 90 from the dispensed DEF determination circuit 142 and/or fault code indicative of the non-dosing status. In response to receiving a non-dosing status for one or more of the plurality of DEF dosing systems 90, the compensation circuit 150 can allocate the commanded amount of DEF between the one or more DEF dosing systems 90 having the dosing status to compensate for at least some of the DEF that is not being delivered to the exhaust gas stream. For example, the compensation circuit 150 can increase the amount of DEF that is injected by the one or more DEF dosing systems 90 having the dosing status. In some embodiments, the compensation circuit 150 is structured to activate auxiliary DEF pumps and/or auxiliary DEF dosers in response to receiving the fault generated by the deficit determination circuit 146. In some embodiments, the compensation circuit 150 is structured to change one or more engine operating parameters in response to receiving the fault generated by the deficit determination circuit 146. In some embodiments, the compensation circuit 150 can change engine operation parameters to operate the engine 18 under conditions that produce less NOx in response to receiving the fault generated by the deficit determination circuit 146. For example, the compensation circuit 150 can derate the engine 18 (e.g., reduce a power output of the engine 18).

In some embodiments, the deficit determination circuit 146 is structured to determine an amount of time that the vehicle 10 operates under conditions in which the DEF variable is at or above the predetermined threshold. In such an embodiment, the deficit determination circuit 146 is structured to increment a counter by a value of a predetermined time period in response to determining that the value of the DEF variable exceeds the predetermined threshold. The deficit determination circuit 146 is structured to not increment the counter by the value of the predetermined time period in response to determining that the value of the DEF variable is less than the predetermined threshold.

In some embodiments, the deficit determination circuit 146 can decrease the value of the DEF variable in response to the DEF dosing system 90 having the non-dosing status self-correcting (e.g., pump 94 pressure increases above the minimum pressure threshold, a blockage in the doser 62 passes, etc.). After self-correction of the DEF dosing system 90 having the non-dosing status, the actual amount of DEF injected into the exhaust gas stream can be substantially the same as the commanded dose of DEF. The deficit determination circuit 146 the decrements the value of the DEF variable by the value of the decrement value, causing the value of the DEF variable to be below the predetermined threshold. The deficit determination circuit 146 does not increment the counter by the value of the predetermined time period when the value of the DEF variable is below the predetermined threshold. In another example, the DEF variable can decrease in response to the compensation circuit 150 and/or the DEF command circuit 138 allocating the dosing command across the DEF dosing systems 90 having the dosing status, and/or the compensation circuit 150 activating auxiliary dosing systems such that the actual amount of DEF injected into the exhaust gas stream can be substantially the same as the commanded amount of DEF. The deficit determination circuit 146 then decrements the DEF variable by the value of the decrement value, causing the value of the DEF variable to be below the predetermined threshold. The deficit determination circuit 146 does not increment the counter by the value of the predetermined time period when the value of the DEF variable is below the predetermined threshold. In another example, the DEF command circuit 138 can reduce the commanded amount of DEF in response to the change in engine operating conditions initiated by the compensation circuit 150 such that the actual amount of DEF injected into the exhaust gas stream can be substantially the same as the commanded dose of DEF. The counter is then decremented by value of the decrement value, causing the value of the counter to be below the predetermined threshold. The deficit determination circuit 146 does not increment the counter by the value of the predetermined time period when the value of the counter is below the predetermined threshold.

FIG. 4 illustrates a method 230 for determining an amount of time that the DEF variable is at or above the predetermined threshold according to an exemplary embodiment. The method 230 starts after the value of the DEF variable has exceeded the predetermined threshold at least once. The vehicle 10 can operate according to the method 230 after the value of the counter has been greater than or equal to the deficit value. At process 234, the deficit determination circuit 146 compares the counter to the predetermined threshold to determine whether the counter has fallen below the predetermined threshold. At process 236, in response to determining that the counter has fallen below the predetermined threshold, the deficit determination circuit does not increment the counter. At process 238, in response to determining that the DEF variable is greater than or equal to the deficit threshold, the deficit determination circuit 146 generates a fault indicating that an unwanted consequence may occur, such as the engine 18 not or possibly not meeting one or more emissions standards. At process 242, the deficit determination circuit 146 increments the value of the counter based on the value (e.g., length or duration) of the predetermined time period.

FIG. 5 illustrates a method 262 for determining an amount of time that that the commanded amount of DEF dispensed is less than the actual amount of DEF dispensed according to another exemplary embodiment. The method 262 starts after the value of the DEF variable has exceeded the predetermined threshold at least once. The vehicle 10 can operate according to the method 262 after the value of the DEF variable has been greater than or equal to the deficit value. At process 264, the deficit determination circuit 146 compares the DEF variable to the predetermined threshold to determine whether the DEF variable has fallen below the predetermined threshold. At process 266, in response to determining that the DEF variable has fallen below the predetermined threshold, the deficit determination circuit does not increment the counter. At process 268, in response to determining that the DEF variable is greater than or equal to the predetermined threshold, the deficit determination circuit 146 generates a fault indicating that an unwanted consequence may occur, such as the engine not or possibly not meeting one or more emissions standards. At process 270, the deficit determination circuit 146 increments the value of the counter based on the value of the predetermined time period. At process 272, the compensation circuit 150 changes the engine operating parameters of the engine 18. For example, the compensation circuit 150 may derate the engine 18 to reduce an amount of NOx produced by the engine 18. Although processes 272 is illustrated as occurring after process 268, process 272 can occur at any time after any of the DEF dosing systems 90 has a non-dosing status. At process 274, the DEF command circuit 138 receives information indicative of the concentration of NOx in the exhaust gas stream. At process 276, the DEF command circuit 138 determines a commanded amount of DEF to dispense to the exhaust gas stream. The commanded amount of DEF generated by process 276 is less than the commanded amount of DEF generated by the method 160 because the engine 18 is operating at conditions that produce less NOx during process 276 because the engine 18 is operating under the engine operating parameters that were changed at process 272. At process 278, the method 262 begins process 164 of the method 160.

FIG. 6 illustrates a plot 282 of the first DEF dispensing system 82 operating in accordance with the method 230 of FIG. 4 or the method 262 FIG. 5. Line 286 indicates a value of the DEF variable. As indicated by the line 286, the value of the DEF variable is substantially equal to the value of the predetermined threshold, which is shown as DT in FIG. 6, from 0-20 seconds, 40-50 seconds, and after 65 seconds (e.g., during the horizontal portions of the line 286). The value of the DEF variable is less than the predetermined threshold from 20 seconds-40 seconds and 50 seconds-65 seconds. Line 290 indicates a conventional timing variable indicative of an amount of time that that the commanded amount of DEF dispensed is less than the actual amount of DEF dispensed. As indicated by the line 290, the conventional timing variable is incremented for each of the predetermined time periods that occur after the value of the DEF variable is first greater than or equal to the predetermined threshold. Accordingly, the value of the conventional timing variable can overestimate the amount of time that the DEF variable is above the predetermined threshold. For example, the line 290 increases between 20 seconds-40 seconds and between 50 seconds-65 seconds despite the fact that the DEF variable is less than the predetermined threshold during these time periods. Line 294 indicates the timing variable of the present disclosure. As described above, the timing variable of the present disclosure is indicative of the amount of time that that the commanded amount of DEF dispensed is less than the actual amount of DEF dispensed. As indicated by the line 294, the timing variable is incremented by the deficit determination circuit 146 when the value of the DEF variable is greater than or equal to the predetermined threshold. The timing variable is not incremented when the value of the DEF variable is less than the predetermined threshold, as shown by line 294. The line 294 is flat between 20 seconds-40 seconds and 50 seconds-65 seconds. Accordingly, the counter of the present disclosure can provide a more accurate estimate of the amount of time that that the commanded amount of DEF dispensed is less than the actual amount of DEF dispensed.

FIG. 7 illustrates operation of the first DEF dispensing system 82 according to an exemplary embodiment in which the plurality of pumps 94 are pressurized throughout the illustrated time period. The plurality of pumps 94 includes a first pump, a second pump, and a third pump. Plot 298 illustrates a pressure of the first pump (line 302), a pressure of the second pump (line 306), and a pressure of the third pump (line 310). As illustrated in plot 298, the first pump, the second pump, and the third pump are pressurized (e.g., have a pressure above the minimum pressure threshold) and remain pressurized throughout the illustrated time period. Plot 314 illustrates a commanded amount of DEF (line 316) and an actual amount of DEF dispensed to the exhaust gas stream. The actual amount of DEF dispensed to the exhaust gas stream is illustrated for each pump. Line 318 indicates the actual amount of DEF dispensed by the first pump, line 322 indicates the actual amount of DEF dispensed by the second pump, and line 326 indicates the actual amount of DEF dispensed by the third pump. As illustrated in plot 314, the first pump, the second pump, and the third pump inject substantially a same amount of DEF into the exhaust gas stream. Plot 330 indicates an accumulated amount of DEF that has not been dosed during the illustrated time period. As indicated in plot 330, the accumulated amount of DEF not dispensed is substantially zero since the pumps dispense the commanded amount of DEF during the illustrated time period. Plot 334 illustrates an amount of time in which the actual amount of DEF dispensed is less than the commanded amount of DEF dispensed. In the illustrated embodiment, the amount of time in which the actual amount of DEF dispensed is less than the commanded amount of DEF dispensed (line 336) is substantially zero since the pumps dispense the commanded amount of DEF during the illustrated time period.

FIG. 8 illustrates operation of the first DEF dispensing system 82 according to an exemplary embodiment in which one of the plurality of pumps 94 has a pressure below the minimum pressure threshold (e.g., drops out). The plurality of pumps 94 includes a first pump, a second pump, and a third pump. Plot 338 illustrates a pressure of the first pump (line 342), a pressure of the second pump (line 346), and a pressure of the third pump (line 350). As illustrated in plot 338, the first pump and the second pump are pressurized and remain pressurized throughout the illustrated time period. As indicated by arrow 354, a pressure of the third pump is substantially zero during a portion of the illustrated time period. Plot 358 illustrates a commanded amount of DEF (line 362) and an actual amount of DEF dispensed to the exhaust gas stream. The actual amount of DEF dispensed to the exhaust gas stream is illustrated for each pump. Line 366 indicates the actual amount of DEF dispensed by the first pump, line 370 indicates the actual amount of DEF dispensed by the second pump, and line 374 indicates the actual amount of DEF dispensed by the third pump. As illustrated by arrow 378, the third pump injects substantially no DEF into the exhaust gas stream when the third pump is depressurized (e.g., has a pressure below the minimum pressure threshold). An amount of DEF dispensed by the first and second pumps has been increased to compensate for the loss of pressure to the third pump. As illustrated in the plot 358, the first pump, the second pump, and the third pump inject substantially the same amount of DEF into the exhaust gas stream when the three pumps are pressurized. Plot 382 indicates an accumulated amount of DEF not dosed. As indicated in plot 382, in the illustrated embodiment, the accumulated amount of DEF not dosed increases at substantially the same time as the third pump is depressurized. The amount of DEF not dosed begins increasing when the third pump becomes depressurized and continues increasing until the pressure to the third pump has been restored. Point 386 indicates the time at which the cumulative difference between the commanded amount of dispensed DEF and the actual amount of dispensed DEF exceeds the value of the predetermined threshold. Plot 390 illustrates an amount of time in which the actual amount of DEF dispensed is less than the commanded amount of DEF dispensed and illustrates when a fault code is displayed. Line 394 indicates the time that the actual amount of DEF dispensed is less than commanded amount of DEF dispensed to the exhaust gas stream. As indicated by the arrow 398, the time that the DEF dosing requirement is not met corresponds to the time period at which the third pump is not pressurized. Plot 402 indicates a time that fault code is displayed. As indicated by arrow 406, the fault code is displayed at substantially the same time as point 386, which indicates the time at which the amount of DEF that is not dosed exceeds the predetermined threshold. As shown by the plot 402, the fault code remains displayed until the end of the illustrated time period.

FIG. 9 illustrates operation of the first DEF dispensing system 82 according to an exemplary embodiment in which two of the plurality of pumps 94 have a pressure below the minimum pressure threshold (e.g., drop out). The plurality of pumps 94 includes a first pump, a second pump, and a third pump. Plot 410 illustrates a pressure of the first pump (line 414), a pressure of the second pump (line 418), and a pressure of the third pump (line 422). As illustrated in plot 410, the first pump is pressurized and remains pressurized throughout the illustrated time period. As indicated by arrow 426, a pressure of the second pump and the third pump are substantially zero during a portion of the illustrated time period. Plot 430 illustrates a commanded amount of DEF (line 434) and an actual amount of DEF dispensed to the exhaust gas stream. The actual amount of DEF dispensed to the exhaust gas stream is illustrated for each pump. Line 438 indicates the actual amount of DEF dispensed by the first pump, line 442 indicates the actual amount of DEF dispensed by the second pump, and line 446 indicates the actual amount of DEF dispensed by the third pump. Arrow 450 indicates a time period at which the second pump and the third pump inject substantially no DEF into the exhaust gas stream. An amount of DEF dispensed by the first pump has been increased to compensate for the loss of pressure to the second pump and the third pump. The first pump, the second pump, and the third pump inject substantially a same amount of DEF into the exhaust gas stream during times at which all of the pumps are pressurized. Plot 454 indicates an accumulated amount of DEF not dosed. As indicated in plot 454, the difference between the commanded amount of DEF dispensed and the actual amount of DEF dispensed begins increasing when the first pump and the second pump depressurize and continues increasing until the pressure to the second pump and the third pump is restored. Point 458 indicates the time at which the amount of DEF not dosed exceeds the value of the deficit threshold. Plot 462 illustrates an amount of time in which the actual amount of DEF dispensed is less than the commanded amount of DEF dispensed and a time in which a fault code is displayed. Line 466 indicates the time that the DEF dosing requirement is not met. The line 466 is non-zero at a time period corresponding to the time period at which the second pump and the third pump are not pressurized. Line 470 indicates the fault code. The fault code is displayed at substantially the same time as the point 458, which indicates the time at which the amount of DEF that is not dosed exceeds the predetermined threshold. As shown by line 470, the fault code remains until the end of the illustrated time period.

FIG. 10 illustrates operation of the first DEF dispensing system 82 according to an exemplary embodiment in which one of the plurality of pumps 94 has a pressure below the minimum pressure threshold (e.g., drops out) twice during the illustrated time period. The plurality of pumps 94 includes a first pump, a second pump, and a third pump. Plot 474 illustrates a pressure of the first pump (line 478), a pressure of the second pump (line 482), and a pressure of the third pump (line 486). As illustrated in plot 474, the first pump and the second pump are pressurized and remain pressurized throughout the illustrated time period. As indicated by arrow 490, a pressure of the third pump is substantially zero during a first portion of the illustrated time period and, as illustrated by arrow 480, during a second portion of the illustrated time period. Plot 498 illustrates a commanded amount of DEF (line 502) and an actual amount of DEF dispensed to the exhaust gas stream. The actual amount of DEF dispensed to the exhaust gas stream is illustrated for each pump. Line 506 indicates the actual amount of DEF dispensed by the first pump, line 510 indicates the actual amount of DEF dispensed by the second pump, and line 514 indicates the actual amount of DEF dispensed by the third pump. Arrow 490 indicates a first time period in which the third pump injects substantially no DEF into the exhaust gas stream. Arrow 494 indicates a second time period in which the third pump injects substantially no DEF into the exhaust gas stream. The first pump, the second pump, and the third pump inject substantially a same amount of DEF into the exhaust gas stream when the three pumps are pressurized. An amount of DEF dispensed by the first and second pumps has been increased to compensate for the loss of pressure to the third pump during both instances that the third pump drops out. After each dropout, the third pump is again pressurized, and each of the first pump, the second pump, and the third pump inject DEF into the exhaust gas stream. Plot 518 indicates an accumulated amount of DEF not dosed. As indicated in plot 518, the accumulated amount of DEF not dosed increases at substantially a same time as the third pump is depressurized. During the first dropout of the third pump, the accumulated quantity of NOx that is not dosed (e.g., the value of the DEF variable) is below the value of the deficit value despite the dropout of the third pump. The accumulated quantity of NOx that is not dosed remains constant once the third pump resumes pumping. With continued reference to plot 518, the accumulated quantity of NOx that is not dosed increases during the second dropout of the third pump. Point 522 indicates the time at which the amount of DEF difference between the commanded amount of DEF dispensed and the actual amount of DEF dispensed (e.g., the value of the DEF variable) exceeds the value of the predetermined threshold. Plot 526 illustrates an amount of time in which the actual amount of DEF dispensed is less than the commanded amount of DEF and a fault code. Line 530 indicates that the amount of DEF dispensed is less than the commanded amount of DEF during the first dropout of the third pump and the second dropout of the third of the third pump. Line 534 indicates a time at which the fault code is displayed. As indicated by the line 534, a fault is not displayed during the first dropout of the third pump because the amount of DEF that is not dosed during the first dropout of the third pump is below the value of the threshold variable. The fault is displayed at substantially the same time as the point 522 at which the amount of DEF that is not dosed (e.g., the value of the DEF variable) exceeds the predetermined threshold. As shown by line 534, the fault code remains until the end of the illustrated time period.

While FIGS. 3-10 describe and illustrate the first DEF dispensing system 82, the second DEF dispensing system 86 can be controlled by the circuits 138-150 in the same manner as described above with respect to the first DEF dispensing system 82.

No claim element herein is to be construed under the provisions of 35 U.S.C. § 112(f), unless the element is expressly recited using the phrase “means for.”

For the purpose of this disclosure, the term “coupled” means the joining or linking of two members directly or indirectly to one another. Such joining may be stationary or moveable in nature. For example, a propeller shaft of an engine “coupled” to a transmission represents a moveable coupling. Such joining may be achieved with the two members or the two members and any additional intermediate members. For example, circuit A “coupled” to circuit B may signify that circuit A communicates directly with circuit B (i.e., no intermediary) or communicates indirectly with circuit B (e.g., through one or more intermediaries).

While various circuits with particular functionality are shown in FIG. 2, it should be understood that the controller 26 may include any number of circuits for completing the functions described herein. For example, the activities and functionalities of the circuits 138-150 may be combined in multiple circuits or as a single circuit. Additional circuits with additional functionality may also be included. Further, the controller 26 may further control other activity beyond the scope of the present disclosure.

As mentioned above and in one configuration, the “circuits” may be implemented in machine-readable medium for execution by various types of processors, such as the processor 130 of FIG. 2. An identified circuit of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions, which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified circuit need not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the circuit and achieve the stated purpose for the circuit. Indeed, a circuit of computer readable program code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within circuits, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network.

While the term “processor” is briefly defined above, the term “processor” and “processing circuit” are meant to be broadly interpreted. In this regard and as mentioned above, the “processor” may be implemented as one or more general-purpose processors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), digital signal processors (DSPs), or other suitable electronic data processing components structured to execute instructions provided by memory. The one or more processors may take the form of a single core processor, multi-core processor (e.g., a dual core processor, triple core processor, quad core processor, etc.), microprocessor, etc. In some embodiments, the one or more processors may be external to the apparatus, for example, the one or more processors may be a remote processor (e.g., a cloud based processor). Alternatively or additionally, the one or more processors may be internal and/or local to the apparatus. In this regard, a given circuit or components thereof may be disposed locally (e.g., as part of a local server, a local computing system, etc.) or remotely (e.g., as part of a remote server such as a cloud based server). To that end, a “circuit” as described herein may include components that are distributed across one or more locations.

Although the diagrams herein may show a specific order and composition of method steps, the order of these steps may differ from what is depicted. For example, two or more steps may be performed concurrently or with partial concurrence. Also, some method steps that are performed as discrete steps may be combined, steps being performed as a combined step may be separated into discrete steps, the sequence of certain processes may be reversed or otherwise varied, and the nature or number of discrete processes may be altered or varied. The order or sequence of any element or apparatus may be varied or substituted according to alternative embodiments. All such modifications are intended to be included within the scope of the present disclosure as defined in the appended claims. Such variations will depend on the machine-readable media and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure.

The foregoing description of embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from this disclosure. The embodiments were chosen and described in order to explain the principles of the disclosure and its practical application to enable one skilled in the art to utilize the various embodiments and with various modifications as are suited to the particular use contemplated. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the embodiments without departing from the scope of the present disclosure as expressed in the appended claims.

Accordingly, the present disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the disclosure is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope. 

What is claimed is:
 1. An apparatus, comprising: a diesel exhaust fluid (DEF) command circuit structured to determine a commanded amount of DEF dispensed to an exhaust gas stream; a dispensed DEF determination circuit structured to determine an actual amount of DEF dispensed to the exhaust gas stream; a deficit determination circuit structured to: determine a difference between the commanded amount of DEF and the actual amount of DEF; determine a value of a DEF variable indicative of amount of DEF dispensed over a predetermined time period; compare the value of the DEF variable to a predetermined threshold; and indicate a fault alert in response to the value of the DEF variable exceeding the predetermined threshold.
 2. The apparatus of claim 1, wherein the dispensed DEF determination circuit is structured to receive information indicative of a status of at least one DEF dosing system structured to dispense the commanded amount of DEF to the exhaust gas stream and determine the actual amount of DEF dispensed to the exhaust gas stream based on the information indicative of the status of the at least one DEF dosing system.
 3. The apparatus of claim 2, wherein the actual amount of DEF dispensed is determined based on an amount of DEF dosing systems having a dosing status, an amount of time that the DEF dosing systems having the dosing status are dispensing DEF, and a commanded flow rate of DEF.
 4. The apparatus of claim 1, further comprising a compensation circuit structured to receive information indicative of a non-dosing status of at least one DEF dosing system of a plurality of DEF dosing systems structured to dispense the commanded amount of DEF to the exhaust gas stream and increase an amount of DEF dispensed by other DEF dosing systems of the plurality of DEF dosing systems in response to receiving the information indicative of the non-dosing status.
 5. The apparatus of claim 1, wherein in response to the DEF variable being a non-zero number and the difference being substantially zero, the deficit determination circuit is structured to decrement the DEF variable by a predetermined amount.
 6. The apparatus of claim 1, wherein the fault alert is indicative of a cumulative effect of the value of the DEF variable exceeding the predetermined threshold.
 7. A system, comprising: a plurality of diesel exhaust fluid (DEF) dosing systems in fluid communication with an exhaust gas stream, the plurality of DEF dosing systems structured to provide DEF to the exhaust gas stream; a controller structured to: determine a commanded amount of DEF dispensed to the exhaust gas stream; determine an actual amount of DEF dispensed to the exhaust gas stream; determine a difference between the commanded amount of DEF and the actual amount of DEF; determine a value of a DEF variable indicative of an amount of DEF not dosed over a predetermined time period; compare the value of the DEF variable to a predetermined threshold; and indicate a fault alert in response to the value of the DEF variable exceeding the predetermined threshold.
 8. The system of claim 7, wherein the controller is structured to receive information indicative of a status of at least one DEF dosing system of the plurality of DEF dosing systems and determine the actual amount of DEF dispensed to the exhaust gas stream based on the information indicative of the status of the at least one DEF dosing system.
 9. The system of claim 8, wherein the actual amount of DEF dispensed is determined based on an amount of DEF dosing systems having a dosing status, an amount of time that the DEF dosing systems having the dosing status are dispensing DEF, and a commanded flow rate of DEF.
 10. The system of claim 7, wherein the controller is further structured to receive information indicative of a non-dosing status of at least one DEF dosing system of the plurality of DEF dosing systems and increase an amount of DEF dispensed by other DEF dosing systems of the plurality of DEF dosing systems in response to receiving the information indicative of the non-dosing status.
 11. The system of claim 7, wherein the controller is further structured to determine an amount of time that the actual amount of DEF is less than the commanded amount of DEF.
 12. The system of claim 7, wherein the DEF variable is a cumulative volume of DEF that has not been dispensed.
 13. The system of claim 7, wherein the controller is structured to decrement the DEF variable by a predetermined amount in response to the DEF variable being a non-zero number and the difference being substantially zero.
 14. The system of claim 7, wherein the fault alert is indicative of a cumulative effect of the value of the DEF variable exceeding the predetermined threshold.
 15. A method, comprising: determining a commanded amount of DEF dispensed to an exhaust gas stream by a plurality of diesel exhaust fluid (DEF) dosing systems in fluid communication with the exhaust gas stream; determining an actual amount of DEF dispensed to the exhaust gas stream by the plurality of DEF dosing systems; determining a difference between the commanded amount of DEF and the actual amount of DEF dispensed to the exhaust gas stream by the plurality of DEF dosing systems; determining a value of a DEF variable indicative of an amount of DEF not dispensed over a predetermined time period; comparing the value of the DEF variable to a predetermined threshold; and indicating a fault alert in response to the value of the DEF variable exceeding the predetermined threshold.
 16. The method of claim 15, further comprising: receiving information indicative of a non-dosing status of at least one DEF dosing system of the plurality of DEF dosing systems; and increasing an amount of DEF dispensed by other DEF dosing systems of the plurality of DEF dosing systems in response to receiving the information indicative of the non-dosing status.
 17. The method of claim 15, further comprising receiving information indicative of a status of at least one DEF dosing system of the plurality of DEF dosing systems and determining the actual amount of DEF dispensed to the exhaust gas stream based on the information indicative of the status of at least one of the DEF dosing systems
 18. The method of claim 17, wherein the actual amount of DEF dispensed is determined based on an amount of DEF dosing systems having a dosing status, an amount of time that the DEF dosing systems having the dosing status are dispensing DEF, and a commanded flow rate of DEF.
 19. The method of claim 15, further comprising determining an amount of time that the actual amount of DEF is less than the commanded amount of DEF.
 20. The method of claim 15, wherein the DEF variable is a cumulative volume of DEF that has not been dispensed. 